[ntp:questions] ISP bloked port 123

David Lord snews at lordynet.org
Wed Sep 18 09:42:22 UTC 2013

Bert Gøtterup Petersen wrote:
> David,
> I understand that a Raspberry-Pi would do the trick, and I am sure that would work  for everyone reading this.
> However, to our customers and installers this would be rather invasive. They are buying/installing a TV not an IT system..
> Our accuracy requirement are not impressive, merely to allow the product to talk to our cloud service (UTC +-5min).
> Our assumption is that some ISP block the port to prevent their customers from running a public NTP server.
> At the moment our best bet seem to be using 'ntpdate' on a different port at regular intervals. From a SW perspective, this is not nice nor elegant, but it would do the trick...


when I used dialup I used sntp port=37 to get the time
(to within about +/- 1 sec IIRC). My ntpd servers will still
accept requests to port 37 although when I was monitoring
the number of requests I was serving those for port 37 were
  << 1% of the total.


More information about the questions mailing list